Split items/ and trainers/ into their data/ and engine/ components

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/tyranitar.asm

@@ -0,0 +1,10 @@
+; TyranitarPokedexEntry: ; 0x1d177b
+	db "ARMOR@" ; species name
+	dw 607, 4450 ; height, weight
+
+	db   "In just one of its"
+	next "mighty hands, it"
+	next "has the power to"
+	page "make the ground"
+	next "shake and moun-"
+	next "tains crumble.@"